Method for bending and/or tempering sheet glass and bending frame therefor

ABSTRACT

For a method for bending and tempering glass which has an opening, the glass is bent in the horizontal position using a bending frame (9) and is tempered on the bending frame (9). The bending frame in respect of its contour and of its geometric shape corresponds to the desired shape of the bent glass. During the bending operation and during the tempering operation the glass is supported, in the region around the edge of the opening, by an additional internal bending frame (12).

TECHNICAL FIELD

The present invention relates to a method for bending and/ortransporting and/or tempering glass with an opening, in a horizontalposition, with the use of a bending frame supporting the glass along itsentire periphery, having a geometric shape corresponding to the contourand to the desired shape of the glass. The invention also deals with abending frame intended for carrying out the method.

BACKGROUND ART

In the usual methods for bending and tempering glass, as used, forexample, in manufacturing curved motor vehicle glass, the glass to bebent is heated up to the bending temperature in the horizontal positioninside a continuous furnace, is bent in a bending station and is heattempered in a tempering station which follows, by rapid cooling in air.In all the known methods of this type bending frames which correspond inrespect of their geometric configuration to the desired shape of theglass to be manufactured are used for the bending and/or fortransporting the bent glass and/or for tempering. For example, suchbending frames are used in the method known by the name of gravitybending as described in document DE 2 945 776 C2. In the case of thismethod, the flat glass to be bent is lifted up by a suction head, isdeposited on such a bending frame and is conveyed therewith into thetempering station. In the case of the method known as compressionbending, such bending frames are used as peripheral bending forms withwhich the glass is pressed against a convex upper bending form whichcovers the entire surface. In a conventional embodiment of thecompression bending method, the bent glass is passed through a temperingstation situated downstream with the aid of this bending frame used as abending form. In another known embodiment of the compression bendingmethod the glass pressed with such a bending frame is held by suctionagainst the upper bending form and after the bending frame has beenremoved it is deposited on another frame with which it is thentransported to the tempering station. There are also known methods forbending and tempering glass in which such bending frames are used onlyfor transporting bent glass, while the bending force in the bendingstation is applied using other means, for example a flow of hot airflowing upwards or using press tools which cover the entire surface.

Insofar as such bending frames are used as frames for carrying the glassinto the tempering station, they are provided, on their upper side, withprojections or with recesses so that the blown air directed against thelower face of the glass can reach the region around the edge of theglass and thus cool this point rapidly enough to obtain the requiredtempering.

It has become evident that the known methods, in which the glass in itssoftened bendable state is bent with known bending frames and/or iscarried by these, do not always lead to optimum results. In particular,when bending and/or tempering glass with an opening formed inside itsface, it may happen that the bent glass exhibits in its bent profilediscontinuities which have a disturbing optical effect. The presence ofone or more openings inside the glass, which also in some circumstanceshave larger dimensions, may, however, be desired, for example whentransmitters or receivers of signals have to be arranged inside theglass for electromagnetic radiation which is excessively attenuated ifit has to pass through the glass. The discontinuities in the bentprofile occurring in the case of glass provided with openings may ariseboth during the bending operation proper and after the bending operationproper, under the effect of gravity on the glass, while the glass isresting in the deformable state on the bending frame.

DISCLOSURE OF THE INVENTION

The object of the invention is to provide a method of the type mentionedin the preamble but which allows glass provided with an opening to bebent and/or tempered by means of a conventional bending installation ora conventional bending and tempering installation without bendingdiscontinuities and/or deformations which are disturbing from theoptical point of view appearing within the glass, particularly aroundthe opening in the glass.

This objective is achieved according to the invention by the fact thatthe glass is mechanically supported in the region around the edge of theopening in the glass by support elements acting along the surface of thedesired shape for the glass during the bending operation and/or duringtransportation from the bending station to the tempering station and/orduring the tempering operation.

Particularly advantageously, the method according to the invention maybe carried out in such a way that the glass, in the region around theedge of the opening in the glass, is supported by a support element inthe form of a frame which supports the region around the edge of theopening in the glass along its entire periphery. As an alternative, theglass may also be supported in the region around the edge of the openingin the glass by a support element in the form of a plate which coversthe entire surface, the shape of which corresponds to the opening in theglass, but which is a bit larger than this opening so that the regionaround the edge of the glass surrounding the opening rests on thissurface along its entire length.

In an alternative form according to the invention, the glass issubjected to compression bending, that is to say that during the bendingstage, the glass supported by the bending frame is pressed against aconvex upper form, covering the entire surface of the glass. This upperform therefore advantageously presses the glass, and more specificallythe region around the edge of the opening, against the support elementsacting on the said edge region.

It has become evident that it is possible, using the method inaccordance with the invention, to confer a defect-free bent shape evenupon glass which has a relatively large opening, something which isparticularly difficult to achieve when the opening is close to the edgeof the glass.

The aim of the invention is also to obtain bent and/or tempered glasscontaining an opening, and in which the discontinuous faces, on accountof the opening, have a continuous curvature. According to the invention,the glass although it has an opening and therefore discontinuous faces,has a continuous bent profile and therefore presents no defects aroundthe edge of the opening which may lead to disturbing optical effects.

The opening could be intended to receive a transmitter and/or receiverof signals, such as a brake light, the latter being fixed so that itlies flush with at least one surface of the said glass, on the peripheryof the opening. It is thus possible to set a transmitter and/or areceiver in, without needing the presence of a frame or molding actingas an insert between the transmitter and/or the receiver and theperiphery of the opening; such inserts would have to be used to concealdefects in curvature around the hole and provide a seal againstmoisture, air and/or light if the glass were obtained according to theknown bending techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the method in accordance with theinvention will emerge from the dependent claims and from the followingdescription of one preferred embodiment of an appropriate bending framefor the method according to the invention given with reference to theattached drawings.

In the drawings:

FIG. 1 shows glass, with an opening, which is to be bent spherically andtempered, and

FIG. 2 shows a bending frame according to the invention for bending andtempering the glass represented in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

In the case of the glass 1 represented in FIG. 1, this is a motor carrear screen which is provided, in its upper part, with an opening 2. Theopening 2 is to be used for the installation of an additional brakelight which is to be fixed into this opening. The opening 2 in the glassis advantageously cut using a high-pressure water jet cutter with X-Yposition control, the high-pressure water jet also containing anappropriate abrasive, for example in the form of corundum particles.

Openings of this type may be made using high-pressure water jet cutterswhich are commercially common, it of course being possible for othermethods and devices according to the state of the art also to be usedfor cutting out the opening 2.

The glass 1 is to be bent according to the gravity bending method into aspherical shape and then heat tempered by rapid blowing of air. In thisbending method, the flat glass with the opening 2 is heated in thehorizontal position to the bending temperature in a continuous furnace,is grasped and raised when it has reached the bending temperature by aflat displaceable suction head and is conveyed using the suction headuntil it is vertically above a bending frame according to the invention,then released by the suction head above the bending frame. The glasstherefore falls onto the bending frame and becomes applied thereto underthe effect of the kinetic energy of dropping it and its self weight.

Because in this case the bending frame is, at the same time, used as atransport frame for transporting the bent glass to the tempering stationand as a frame for carrying it during the tempering process, the bendingframe has to be formed in such a way that the region around the edge ofthe glass is also tempered by the blown flow of air. In theory,constructions known for this such as those described, for example, indocuments EP 0 186 529 B1, WO 93/02017 or U.S. Pat. No. 5,118,335 may bechosen for the configuration of the bending frame.

As FIG. 2 shows, the bending frame 5 is arranged on a carriage 6 whichcan be displaced along rails thanks to the wheels 7 inside a bending andtempering installation. The bending frame 5 comprises a closed outerframe 9, the shape of which corresponds to the contour and desired shapeof the bent glass. The frame 9 is provided, in the known way, on itsinner side, with finger-shaped projections, the spaces between whichform flow channels for the cooling air. Inside the frame 9 at the pointcorresponding to the position of the opening in the glass 2 is a secondframe 12 which is closed on itself. This frame 12 corresponds in respectof its shape and of its size to the shape and size of the opening in theglass 2. It is formed in such a way that on the one hand the edge of theopening in the glass is supported right along its periphery but so that,on the other hand, flow channels are again formed for the blown air bythe presence of projections 13 so that the glass is also rapidly cooledby the blown air on the peripheral surface of the opening in the glassand is thus subjected to compressive stresses. The geometric surfaceshape of the bearing surface of this inner frame 12 has to be designedin accordance with the desired shape of the bent glass so that theglass, when applied against this inner frame 12, also adopts exactly thedesired shape in the region close to the opening 2 without defects whichare disturbing from the optical point of view appearing.

Both the outer frame 9 and the inner frame 12 may respectively be formedas a single piece or constructed of several parts which can be adjustedseparately in terms of height so that subsequent adjustment and finetuning of the bending frame become possible. The inner frame 12 is fixedremovably to the outer frame 9 or to the frame of the carriage 6 byfixing pieces 15, 16. The same bending frame 9 can be used tomanufacture glass with an opening, by optionally attaching the innerframe 12, and glass without an opening after removing the inner frame12. Fixing may also be achieved in such a way that it allows fine tuningor a correction of the position of the frame 12.

We claim:
 1. Method for supporting a glass with an opening, whichcomprises:performing, during a transporting step, one of a bending stepand a tempering step, using a frame having a shape substantiallycorresponding to the contour of the glass, said frame supporting theglass only along its periphery, and separately supporting a regionaround an edge of the opening in the glass.
 2. Bending frame assemblyhaving a shape corresponding to the contour and desired shape of a glasshaving an opening, which comprises:a bending frame supporting the glassonly along its periphery, said frame having a shape substantiallycorresponding to the contour of the glass; and a separate supportelement positioned inside the bending frame and which corresponds to thecontour of the glass in the region corresponding with the region aroundthe edge of the opening in the glass.
 3. Method according to claim 2,which comprises supporting a region around the edge of the opening inthe glass by a support element in the form of a frame which supports theedge of the opening around its entire periphery.
 4. Method according toclaim 1, which comprises supporting during the bending step, the glassby pressing the bending frame against a convex upper form.
 5. Bendingframe assembly according to claim 2, wherein the separate supportelement comprise a second frame which supports the region around theedge of the opening in the glass right around the contour thereof. 6.Bending frame assembly according to claim 2, wherein the support elementcomprises a plurality of parts which are fixed so as to be one ofseparately adjustable and adjustable together in terms of one of heightand of inclination.
 7. Bending frame assembly according to claim 2,wherein the separate support element is removably fixed to the bendingframe corresponding to the contour of the glass.
 8. Bending frameassembly according to claim 2, wherein the separate support element isprovided, on a surface thereof which comes into contact with the glass,with at least one of a plurality projections and teeth which form flowchannels for the blown air required for tempering.
 9. Glass having anopening wherein the glass has discontinuous faces which have acontinuous curvature and said glass comprises one of bent glass andtempered glass.
 10. Method according to claim 1, which comprisespressing, during the bending step, the glass supported by the bendingframe against a convex upper form.
 11. Bending frame assembly accordingto claim 5, wherein the separate support element is removably fixed tothe bending frame corresponding to the contour of the glass.
 12. Bendingframe assembly according to claim 6, wherein the separate supportelement is removably fixed to the bending frame corresponding to thecontour of the glass.
 13. Bending frame assembly according to claim 5,wherein the separate support element is provided, on a surface thereofwhich comes into contact with the glass, with at least one of aplurality of projections and teeth which form flow channels for theblown air required for tempering.
 14. Bending frame assembly accordingto claim 6, wherein the separate support element is provided, on asurface thereof which comes into contact with the glass, with at leastone of a plurality of projections and teeth which form flow channels forthe blown air required for tempering.
 15. Bending frame assemblyaccording to claim 7, wherein the separate support element is provided,on a surface thereof which comes into contact with the glass, with atleast one of a plurality of projections and teeth which form flowchannels for the blown air required for tempering.